X-ray scanning systems have been used for visually inspecting the contents of containers and the inside of enclosed objects quickly compared to the tedious process of manually opening and inspecting an object's contents. In many cases, this improved method of inspection expedites the process and saves time and money for the users of these scanning systems. In some applications, the speed of inspection is a critical parameter that is often a balance between inspection quality, cost, and throughput (or number of objects inspected per minute).
Operator efficiency can be measured as the ratio of image review time versus the total time spent at the operator control station. All tasks not directly supporting image review result in inefficiencies, thereby reducing throughput.
To avoid confusion it is necessary to isolate and associate the image with the suspect article. In current X-ray inspection systems, a queuing conveyor is associated with the main conveyor that transmits the object through the X-ray inspection system. The purpose of the queuing conveyor is to create a physical separation between articles. A physical separation between articles allows for photo-sensor logic to identify discrete articles. Since, the queuing conveyor runs at a slower speed compared to the main conveyor, the speed of the queuing conveyor dictates the throughput of the system.
Image operators must inspect complex images while the image is stationary; thus, the operator may have to stop additional images from being generated on-screen in order to inspect existing images more thoroughly. Currently, to stop the image, the operator invokes a belt stop process. When the belt stops no additional image data is acquired or collected. Current methods usually synchronize the conveyance of objects with the operator's commands to start and stop the images. Due to mechanical and electro-optical limitations of these systems, this synchronization creates delays as the system needs to perform a recovery procedure from each “stop-to-start” transition. This usually results in system latency. Typically, this involves reversing the conveyance mechanism sufficiently and then returning to a constant forward speed to allow the conveyance and electro-optical systems to return to the previous steady state conditions that determine critical inspection quality standards. Therefore, to ensure seamless image presentation, current systems conduct a back-belt process that requires the conveyor belt to reverse for 0.75 seconds before the belt goes forward and X-rays are generated again. This incurs a 1.5 second delay from the time the image operator presses the forward or resume button on the control panel and time that image data appears once again on the display.
What is therefore needed is a system that decouples the synchronization between cessation of image generation on the display and image acquisition through conveyance of the article. Also needed are methods for compensating for image acquisition inefficiencies involving article separation by the queuing conveyor and the post-stop back belt process, so that throughput is enhanced.